Preparation method and application of Cu-based loaded Mn-Pd-N electrode

Abstract

The invention discloses a preparation method and application of a Cu-based loaded Mn-Pd-N. The prepared electrode can be used as a cathode electrode for preparing ethanol through CO2 electroreduction, has a large specific surface area, high catalyst stability and long service life, and shows good activity and CO2 conversion rate in the electrolysis process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemistry, in particular to a preparation method of a Cu-based Mn-Pd-N electrode and its application in the field of catalyzing carbon dioxide (CO2) electro-reduction to prepare ethanol. BACKGROUND

[0002] Since industrialization, the rapid consumption of fossil fuels has brought a large amount of CO2 gas emissions, which has led to the greenhouse effect. In order to solve this problem, the fixation and conversion of CO2 gas is crucial for the sustainability of energy and the environment. Electro-catalytic CO2 reduction can convert it into high-value fuels and chemicals at room temperature and pressure, which provides an ideal solution for carbon cycle. However, the extremely strong chemical stability of CO2 molecules makes the reaction face problems such as slow electrochemical kinetics and low product selectivity. Therefore, designing a cheap and efficient catalyst is particularly important for the industrial application of electro-catalytic CO2 reduction.

[0003] Ethanol is not only an important chemical raw material, but also a high-performance energy and vehicle fuel. Ethanol is in a pivotal position in the entire industry chain, and almost all industrial ethanol is synthesized by fermentation or ethylene hydration. Electrochemical reaction to reduce carbon dioxide to ethanol has the characteristics of green environmental protection and high purity. Therefore, the preparation of ethanol by reducing carbon dioxide is a current research hotspot. Cu-based catalysts have a wide application prospect in the field of carbon dioxide electro-reduction due to their unique electronic structure and catalytic performance. However, pure Cu catalysts have problems such as poor stability and low product selectivity in the catalytic process. Therefore, how to modify Cu-based catalysts to improve their catalytic performance and stability is a problem that needs to be solved in the industry. SUMMARY

[0004] The present application provides a preparation method of a Cu-based Mn-Pd-N electrode and its application in the reaction of CO2 electro-catalytic generation of ethanol. The Cu-based Mn-Pd-N electrode provided by the present application includes a substrate Cu and a Mn-Pd-N composite material loaded on the surface of the Cu-based catalyst. The Mn-Pd composite material can act as an active site to promote the adsorption and activation of carbon dioxide, and the guanidinium ionic liquid can regulate the electrochemical product process and reduce the activation potential. At the same time, through the synergistic effect with the Cu-based catalyst, the stability and product selectivity of the catalyst are improved. Therefore, the catalyst has a stable structure in the process of electrolyzing CO2, high electrolysis CO2 activity and long service life.

[0005] The first object of the present application is to provide a preparation method of a Cu-based Mn-Pd-N electrode, which includes the following steps:

[0006] (1) Preparation of catalyst slurry: add metal manganese salt, palladium salt and carbon powder into the dispersion emulsion and stir uniformly to obtain slurry A, add nitrogen source into slurry A and stir uniformly to obtain catalyst precursor slurry B, add binder into slurry B and stir uniformly to obtain catalyst slurry;

[0007] (2) Support: coat the obtained catalyst slurry on a Cu mesh, and dry to obtain an electrode precursor;

[0008] (3) Pressing: press the electrode precursor and a hydrophobic film into shape;

[0009] (4) Calcination: calcine the electrode of step (3) under a protective atmosphere to prepare a Mn-Pd-N electrode.

[0010] Further, the slurry A of step (1) further comprises guanidinium ionic liquid.

[0011] The guanidinium ionic liquid in step (1) is a functional ionic liquid, the core feature of which is that the cation part is a guanidinium structure, which has high thermal stability and chemical stability, plays an important role in the regulation and selection of electrochemical products and the reduction of activation potential, and common guanidinium ionic liquids are 1,1,3,3-tetramethyl guanidinium lactate (TMGL), 1,1,2,2-tetramethyl guanidinium trifluoroacetate ([TMG][TFA]), N,N,N',N'-tetramethyl-N"-methyl-N"-butyl guanidinium tetrafluoroborate ([MBTMG]BF4), etc.

[0012] The palladium salt in step (1) is one or more of palladium acetate, palladium nitrate, palladium sulfate and palladium chloride, and the manganese salt is one or more of manganese acetate, manganese nitrate, manganese sulfate and manganese chloride.

[0013] Further, the dispersion emulsion is selected from methylhydroxyethyl cellulose solution and starch solution, preferably methylhydroxyethyl cellulose solution.

[0014] The mass ratio of the guanidinium ionic liquid to the dispersion emulsion is 1:10-1:100; preferably, the mass ratio of the guanidinium ionic liquid to the dispersion emulsion is 1:10-1:60.

[0015] The mass ratio of the palladium salt to the dispersion emulsion is 1:10-1:20; preferably, the mass ratio of the palladium salt to the dispersion emulsion is 1:10-1:15.

[0016] The mass ratio of the manganese salt to the dispersion emulsion is 1:5-1:10; preferably, the mass ratio of the manganese salt to the dispersion emulsion is 1:5-1:8.

[0017] Further, the mass ratio of the carbon powder to the dispersed emulsion in step (1) is 1:20-1:50; preferably, the mass ratio of the carbon powder to the dispersed emulsion is 1:30-1:40.

[0018] Further, the nitrogen source is selected from dicyandiamide, urea, monocyandiamide, amino acid, nitrate, ammonium salt, preferably dicyandiamide.

[0019] Further, the mass ratio of the nitrogen source to the dispersed emulsion in step (1) is 1:10-1:15; preferably, the mass ratio of the nitrogen source to the dispersed emulsion is 1:12-1:15.

[0020] Further, the binder is a polytetrafluoroethylene emulsion or a Nafion solution.

[0021] Further, the mass ratio of the binder to the dispersed emulsion in step (1) is 1:8-1:15; preferably, the mass ratio of the binder to the dispersed emulsion is 1:10-1:12.

[0022] Further, in step (2), the drying temperature is 20-80℃ for 1-6h; preferably, the drying temperature is 40-60℃ and the drying time is 2-3h.

[0023] Further, in step (2), the loading amount of the catalyst slurry is 10-600mg / cm 2 ; preferably, 100-500mg / cm 2 .

[0024] Further, in step (3), the pressure applied in the pressing process is 1-50Mpa; preferably, the pressure applied in the pressing process is 20-40Mpa.

[0025] Further, in step (3), the hydrophobic membrane is a polytetrafluoroethylene membrane.

[0026] Further, in step (4), the protective atmosphere is one or more of nitrogen, inert gas or air.

[0027] Further, in step (4), the temperature is raised at a rate of 10-20℃ / min to 100-260℃ and calcined for 1-40h; preferably, the calcination time is 12-24h.

[0028] The application also provides the application of the Cu-based Mn-Pd-N electrode in the reaction of preparing ethanol by CO2 electrolytic reduction.

[0029] A method for preparing ethanol by CO2 electrolytic reduction, which uses the electrode prepared by the preparation method of the application as a cathode to electrolyze CO2 to prepare ethanol.

[0030] Preferably, the catholyte is a KOH or KHCO3 solution; preferably, the KOH or KHCO3 solution has a concentration of 0.1-2 mol / L, more preferably, the KOH or KHCO3 solution has a concentration of 0.5-1 mol / L;

[0031] Preferably, the anode of the CO2 electrolysis reduction reaction for preparing ethanol is an iridium electrode;

[0032] Preferably, the anolyte of the CO2 electrolysis reduction reaction for preparing ethanol is an H2SO4 solution; preferably, the H2SO4 solution has a concentration of 0.1-1 mol / L, more preferably, the H2SO4 solution has a concentration of 0.2-0.5 mol / L;

[0033] Preferably, a diaphragm is provided in the CO2 electrolysis reduction reaction for preparing ethanol, and the diaphragm comprises a proton exchange membrane;

[0034] Preferably, CO2 is introduced into the catholyte for electrolysis reaction, and the CO2 gas flow rate is 10-50 ml / min, preferably, the flow rate is 20-30 ml / min;

[0035] The current density applied in the CO2 electrolysis reduction reaction for preparing ethanol is 500-5000 A / m 2 , preferably, the current density applied is 1000-2000 A / m 2 ; and / or,

[0036] The electrolysis time of the CO2 electrolysis reduction reaction for preparing ethanol is 1-3 h.

[0037] Compared with the prior art, the beneficial effects of the present application are:

[0038] (1) The present application synthesizes Mn-Pd-N catalyst slurry, and the catalyst is calcined and carbonized on a Cu conductive substrate to form an integrated catalytic electrode, thereby improving the adhesion of the catalytic layer to the hydrophobic layer and the conductive substrate, and significantly enhancing the stability of the catalytic layer;

[0039] (2) The present application sintered electrode by calcination mainly plays a pore-forming role, so that the Mn-Pd-N catalyst is uniformly dispersed on the surface of the electrode, increasing the active sites of the catalyst; nitrogen-containing compounds are added to the catalyst slurry, and nitrogen sites are introduced after carbonization, and the nitrogen coordination enhances the electron density of the manganese center, forming a metal-nitrogen-carbon catalyst layer that promotes CO2 adsorption and reduction and increases the adsorption capacity of CO2, thereby improving the conversion rate of CO2;

[0040] (3) The CO2 electro-reduction ethanol electrode prepared by the present application is doped with guanidinium ionic liquid, which can effectively reduce the activation potential of the electrochemical process product and has an important role in the regulation of the product, greatly improving the Faraday efficiency and selectivity of the ethanol product. Attached Figure Description

[0041] Appendix Figure 1 The graph shows the Faraday efficiency performance of the Cu-based supported Mn-Pd-N catalyst in the electrocatalytic carbon dioxide reduction reaction of Example 2 of the present invention. Detailed Implementation

[0042] The present invention will be further illustrated below with reference to examples, but the present invention is not limited to the following embodiments.

[0043] Raw material source:

[0044] PTFE emulsion (polytetrafluoroethylene emulsion): Inokai Reagent

[0045] Dicyandiamide: Inokai Reagent

[0046] 1,1,3,3-Tetramethylguanidine lactate: CAS No.: 686349-06-4, Xi'an Qiyue Biotechnology Co., Ltd.

[0047] 1,1,2,2-Tetramethylguanidine trifluoroacetate: CAS No.: None, Xi'an Qiyue Biotechnology Co., Ltd.

[0048] N,N,N',N'-Tetramethyl-N"-Methyl-N"-Butylguanidine tetrafluoroborate: CAS No.: 88248-68-4, Xi'an Qiyue Biotechnology Co., Ltd.

[0049] All embodiments in this application have been confirmed to have synthesized ethanol by gas chromatography.

[0050] Example 1:

[0051] (1) Add 1g of manganese nitrate, 1g of palladium nitrate and 0.25g of carbon powder to 10g of methyl hydroxyethyl cellulose solution and stir evenly to obtain slurry A. Add 1g of dicyandiamide to slurry A and stir evenly to obtain catalyst precursor slurry B. Add 1g of PTFE emulsion to slurry B and stir evenly to obtain catalyst slurry.

[0052] (2) Loading: The obtained catalyst slurry was coated onto a Cu mesh and dried at 35°C to obtain the electrode precursor. The catalyst slurry loading was 100 mg / cm². 2 ;

[0053] (3) Pressing: The electrode precursor and PTFE hydrophobic film are pressed into shape at a pressing pressure of 40 MPa.

[0054] (4) Calcination: The electrode (3) is calcined in air atmosphere by a phased heating process, with a heating rate of 15℃ / min, and calcined at 260℃ for 24h to produce a Mn-Pd-N electrode.

[0055] The electrode prepared in this embodiment was used as a CO2 electroreduction cathode material. The catholyte was a 1 mol / L KOH solution, the anode was an iridium-tantalum electrode, and the anolyte was a 0.5 mol / L H2SO4 solution. The CO2 gas flow rate was 30 ml / min, and the anode was set at 2000 A / m². 2 At the given current density, the current efficiency of ethanol reaches 58%.

[0056] Example 2:

[0057] (1) 0.2g of 1,1,3,3-tetramethylguanidine lactate, 1g of manganese nitrate, 1g of palladium nitrate and 0.25g of carbon powder were added to 10g of methyl hydroxyethyl cellulose solution and stirred evenly to obtain slurry A. 1g of dicyandiamide was added to slurry A and stirred evenly to obtain catalyst precursor slurry B. 1g of PTFE emulsion was added to slurry B and stirred evenly to obtain catalyst slurry.

[0058] (2) Loading: The obtained catalyst slurry was coated onto a Cu mesh and dried at 35°C to obtain the electrode precursor. The catalyst slurry loading was 100 mg / cm². 2 ;

[0059] (3) Pressing: The electrode precursor and PTFE hydrophobic film are pressed into shape at a pressing pressure of 25 MPa.

[0060] (4) Calcination: The electrode (3) is calcined in air atmosphere by a phased heating process, with a heating rate of 15℃ / min, and calcined at 260℃ for 24h to produce a Mn-Pd-N electrode.

[0061] The electrode prepared in this embodiment was used as a CO2 electroreduction cathode material. The catholyte was a 1 mol / L KOH solution, the anode was an iridium-tantalum electrode, and the anolyte was a 0.5 mol / L H2SO4 solution. The CO2 gas flow rate was 30 ml / min, and the anode was set at 2000 A / m². 2 At the given current density, the current efficiency of ethanol reaches 73%.

[0062] Example 3:

[0063] (1) Dissolve 0.5g of 1,1,2,2-tetramethylguanidine trifluoroacetate, 0.6g of manganese sulfate, 0.35g of palladium sulfate and 0.15g of carbon powder in 5g of methyl hydroxyethyl cellulose solution and stir evenly to obtain slurry A. Dissolve 0.5g of urea in slurry A and stir evenly to obtain catalyst precursor slurry B. Dissolve 0.5g of PTFE emulsion in slurry B and stir evenly to obtain catalyst slurry.

[0064] (2) Loading: The obtained catalyst slurry was coated onto a Cu mesh and dried at 35°C to obtain the electrode precursor. The catalyst slurry loading was 400 mg / cm². 2;

[0065] (3) Pressing: The electrode precursor and PTFE hydrophobic film are pressed into shape at a pressing pressure of 20 MPa.

[0066] (4) Calcination: The electrode (3) is calcined in air atmosphere by a phased heating process, with a heating rate of 10℃ / min, and calcined at 220℃ for 24h to produce a Mn-Pd-N electrode.

[0067] The electrode prepared in this embodiment was used as a CO2 electroreduction cathode material. The catholyte was a 1 mol / L KOH solution, the anode was an iridium-tantalum electrode, and the anolyte was a 0.5 mol / L H2SO4 solution. The CO2 gas flow rate was 30 ml / min, and the anode was set at 2000 A / m². 2 At the given current density, the current efficiency of ethanol reaches 68.4%.

[0068] Example 4:

[0069] (1) Dissolve 0.1g N,N,N',N'-tetramethyl-N"-methyl-N"-butylguanidine tetrafluoroborate, 1.5g manganese chloride, 1g palladium chloride and 0.35g carbon powder in 10g methyl hydroxyethyl cellulose solution and stir evenly to obtain slurry A. Dissolve 1g dicyandiamide in slurry A and stir evenly to obtain catalyst precursor slurry B. Dissolve 0.8g PTFE emulsion in slurry B and stir evenly to obtain catalyst slurry;

[0070] (2) Loading: The obtained catalyst slurry was coated onto a Cu mesh and dried at 45°C to obtain the electrode precursor. The catalyst slurry loading was 100 mg / cm². 2 ;

[0071] (3) Pressing: The electrode precursor and PTFE hydrophobic film are pressed into shape at a pressing pressure of 30 MPa.

[0072] (4) Calcination: The electrode (3) is calcined in a nitrogen atmosphere by a staged heating process, with a heating rate of 15℃ / min, and calcined at 240℃ for 24h to produce a Mn-Pd-N electrode.

[0073] The electrode prepared in this embodiment was used as a CO2 electroreduction cathode material. The catholyte was a 0.5 mol / L KOH solution, the anode was an iridium-tantalum electrode, and the anolyte was a 0.3 mol / L H2SO4 solution. The CO2 gas flow rate was 30 ml / min, and the anode was set at 2000 A / m². 2 At the given current density, the current efficiency of ethanol reaches 62.6%.

[0074] Comparative Example 1

[0075] The cathode electrode was prepared using the same method as in Example 1, the main difference being that no palladium salt was added.

[0076] The CO2 electrolysis reaction was carried out using the same method as in Example 1, at 2000 A / m 2 At the given current density, the current efficiency of ethanol is 25.7%.

Claims

1. A method for preparing a Cu-based supported Mn-Pd-N electrode, characterized in that, Includes the following steps: (1) Preparation of catalyst slurry: Add manganese salt, palladium salt and carbon powder to the dispersion emulsion and stir evenly to obtain slurry A. Add nitrogen source to slurry A and stir evenly to obtain catalyst precursor slurry B. Add binder to slurry B and stir evenly to obtain catalyst slurry. (2) Supporting: The obtained catalyst slurry is coated on a Cu mesh and dried to obtain the electrode precursor; (3) Pressing: Pressing the electrode precursor and the hydrophobic film into shape; (4) Calcination: The electrode from step (3) is calcined under a protective atmosphere to produce a Mn-Pd-N electrode.

2. The preparation method according to claim 1, characterized in that, Guanidine salt ionic liquid is also added to slurry A in step (1); Preferably, the guanidine salt ionic liquid in step (1) includes one or more of 1,1,3,3-tetramethylguanidine lactate (TMGL), 1,1,2,2-tetramethylguanidine trifluoroacetate ([TMG][TFA]), and N,N,N',N'-tetramethyl-N"-methyl-N"-butylguanidine tetrafluoroborate ([MBTMG]BF4).

3. The preparation method according to claim 1 or 2, characterized in that, The palladium salt mentioned in step (1) is one or more of palladium acetate, palladium nitrate, palladium sulfate, and palladium chloride, and the manganese salt is one or more of manganese acetate, manganese nitrate, manganese sulfate, and manganese chloride. Preferably, the dispersion emulsion is selected from methyl hydroxyethyl cellulose solution and starch solution, with methyl hydroxyethyl cellulose solution being more preferred. Preferably, the mass ratio of the guanidine salt ionic liquid to the dispersion emulsion is 1:10 to 1:100; more preferably, the mass ratio of the guanidine salt ionic liquid to the dispersion emulsion is 1:10 to 1:

60. Preferably, the mass ratio of the palladium salt to the dispersion emulsion is 1:10 to 1:20; more preferably, the mass ratio of the palladium salt to the dispersion emulsion is 1:10 to 1:

15. Preferably, the mass ratio of the manganese salt to the dispersion emulsion is 1:5 to 1:10; more preferably, the mass ratio of the manganese salt to the dispersion emulsion is 1:5 to 1:

8. Preferably, the mass ratio of toner to dispersion emulsion in step (1) is 1:20 to 1:50; more preferably, the mass ratio of toner to dispersion emulsion is 1:30 to 1:

40. Preferably, the nitrogen source is selected from dicyandiamide, urea, monocyandiamide, amino acids, nitrates, and ammonium salts, with dicyandiamide being the most preferred. Preferably, the mass ratio of the nitrogen source to the dispersion emulsion in step (1) is 1:10 to 1:15; preferably, the mass ratio of the nitrogen source to the dispersion emulsion is 1:12 to 1:

15. Preferably, the adhesive is a polytetrafluoroethylene emulsion or a Nafion solution; Preferably, the mass ratio of the binder to the dispersion emulsion in step (1) is 1:8 to 1:15; preferably, the mass ratio of the binder to the dispersion emulsion is 1:10 to 1:

12.

4. The preparation method according to any one of claims 1-3, characterized in that, In step (2), the drying temperature is 20-80℃ for 1-6 hours; preferably, the drying temperature is 40-60℃ and the drying time is 2-3 hours. Preferably, in step (2), the catalyst slurry loading is 10-600 mg / cm³. 2 Preferred concentration: 100-500 mg / cm³ 2 ; Preferably, the pressure applied during the pressing process in step (3) is 1-50 MPa; more preferably, the pressure applied during the pressing process is 20-40 MPa. Preferably, the hydrophobic membrane in step (3) is a polytetrafluoroethylene membrane.

5. The preparation method according to any one of claims 1-4, characterized in that, In step (4), the protective atmosphere is one or more of nitrogen, inert gas, or air; Preferably, in step (4), the temperature is raised to 100-260℃ and calcined for 1-40 hours at a heating rate of 10-20℃ / min; the preferred calcination time is 12-24 hours.

6. The application of the Cu-based supported Mn-Pd-N electrode according to any one of claims 1-5 in the reaction of CO2 electrolytic reduction to prepare ethanol.

7. A method for preparing ethanol by electrolytic reduction of CO2, wherein an electrode prepared by any one of claims 1-5 is used as the cathode to prepare ethanol by electrolytic reduction of CO2.

8. The method according to claim 7, characterized in that, The cathode electrolyte is a KOH or KHCO3 solution; preferably a KOH or KHCO3 solution with a concentration of 0.1-2 mol / L, more preferably a KOH or KHCO3 solution with a concentration of 0.5-1 mol / L. Preferably, the anode for the CO2 electrolytic reduction reaction to prepare ethanol is an iridium electrode; Preferably, the anolyte for the CO2 electrolytic reduction reaction to prepare ethanol is an H2SO4 solution; more preferably, it is an H2SO4 solution with a concentration of 0.1-1 mol / L, and even more preferably, it is an H2SO4 solution with a concentration of 0.2-0.5 mol / L. Preferably, a membrane is provided in the CO2 electrolytic reduction reaction to prepare ethanol, and the membrane includes a proton exchange membrane; Preferably, CO2 is introduced into the cathode electrolyte to carry out the electrolysis reaction, and the CO2 gas flow rate is 10-50 ml / min, preferably 20-30 ml / min; Preferably, the current density applied to the CO2 electrolytic reduction reaction to prepare ethanol is 500-5000 A / m. 2 The preferred applied current density is 1000-2000 A / m. 2 ; Preferably, the electrolysis time for the CO2 electrolytic reduction reaction to prepare ethanol is 1-3 hours.

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